Type element driving mechanism



June 25, 1957 Filed Sept. 8, 1953 T. H. TOEPPEN TYPE ELEMENT DRIVINGMECHANISM 2 Sheets-Sheet l I IATENTOR. THURSTON H. TOEPPEN June 1957 T.H. TOEPPEN TYPE ELEMENT DRIVING MECHANISM Filed Sept. 8, 195

2 SheetsSheet 2 L VEN TOR.

THURSTON H.TOEPPEN "Hubs ATTORNEY United States Patent TYPE ELEMENTDRIVING MECHANISM Thurston H. Toeppen, Hyde Park, N. Y., assignor toInternational Business Machines Corporation, New York, N. Y., acorporation of New York Application September 8, 1953, Serial No.378,724

21 Claims. (Cl. 197-417) This invention relates to typewriters and, moreparticularly, to an improved type bar actuating and impression controlmechanism for a power driven typewriter.

It can be appreciated readily that, in order for a typed page to havethe degree of perfection required in modern business, each of the typedcharacters should have the same color density or color shade regardlessof the size of the characters, and regardless of whether it happens tobe a lower-case or upper-case character.

It can also be appreciated that, as a matter of preference, the operatormay desire to increase or decrease the color density of all charactersas a .group, or to vary the penetration of the various type charactersinto the surface of the work, for example, in paper plate or wax stencilwork.

Also in modern business installations, it is frequently necessary for atypist to produce, in one instance, a plurality of carbon copies,whereas in another instance, she may need only a single, original copy.It is well recognized that, other conditions being equal, the greaterthe number of carbon copies required, the greater the force which mustbe applied to each type bar in order to produce an impression ofadequate color density on the last copy. At the other extreme, a verylight striking force is employed to produce the shallow but uniformpenetration which is desirable in the preparation of certain types oflithographic plates and wax stencils. In any case, it is desirable tomaintain the highest possible degree of uniformity of penetration and/orcolor density at each impression level throughout a selected range.

To achieve this end, it is an object of this invention to provide animproved type bar actuating mechanism. Another object is to provide atype bar actuating mechanism which supplies not only a high degree ofconsistency of operation over a long period of useful life with asuflicient range of striking force to accommodate all types of work, butalso a convenient means of varying the rorce.

If all type bars strike the work with equal force, the density ofimpression will vary inversely with the size of the character; that is,the same striking force which causes a large character such as theletter mfto print lightly will, when applied to a small character suchas the cause it to print with excessive darkness. The prior art machinesof this class have frequently been provided with adjustments whichpermit the striking force of each type bar to be set at any desiredlevel so that the color density of the character on that type bar willmatch the color density of some reference character. This type ofadjustment will hereinafter be called individual impression control.

In the prior art, it has also been common to provide means forincreasing or decreasing the striking force of all type bars as a groupby substantially equal amounts, in order to raise or lower the overalllevel of color density as desired by the operator. This type ofadjustment will hereinafter be referred to as group impression control.

In order to demonstrate the need for other requirements of control, itis first necessary to consider how the color densities of large andsmall characters are differently affected by operation of the groupcontrol adjustment.

It has been shown that different striking forces are required in orderto produce the same level of color density in characters of differentsizes. In conventional machines, the striking forces are increased ordecreased by substantially equal amounts as a result of operation of thegroup control mechanism. Consequently, the color density of the smallcharacters is not changed in the same degree as the large characters. Onthe contrary, a small character will change color considerably more thana large one. In a typical example of the prior art, the characters m andcan be initially adjusted .by means of the individual control so thatthey print with equal, median color density when the group control is atits central position. However, when the group control is advancedtowards its maximum position, the will be much darker and may even bepunching holes in the work at a point where the m is only moderatelydarker than before. On the other hand, when the group control isretracted towards its minimum position, the will be much lighter and mayeven fail to print at a point where the m is only moderately lighterthan at the reference setting. As a result, the color densities of thevarious characters are uniform only at the reference setting, and go outof balance, or lose uniformity, at the upper and lower ends of the groupcontrol scale.

This is a fundamental problem, and has been dealt with in the prior artin two ways. In some cases, the impression range provided by the groupcontrol mechanism has been arbitrarily restricted to a rather smallamount, so that the color densities of the various sizes of charactersdo not get conspicuously out of balance; as a result, the usable rangeis smaller than the desired range. In other cases, the design of thetype is modified so as to increase the effective size of the smallercharacters and reduce the effective size of the larger characters,thereby minimizing the diiferential between them. The most noticeableresult of this approach is the use of abnormally large punctuationmarks, and the consequent loss of typographic quality.

These limitations can be overcome .by providing a group controladjusting means which causes a change in the striking force of the typebar to vary in proportion to the area or size of each characterinvolved, and it is a further object .of this invention to provide animproved structure for this purpose. This may be described as control ofthe rate of change of striking force, and it is hereinafter referred toas gradient control.

Another factor to be considered is the customary practice of placing twocharacters on the head of each type bar, either of which may be selectedby the operator through the use of a shift mechanism of suitable design.The two characters are not ordinarily the same size; in most instances,the upper-case character is somewhat larger, but in many instances, itis smaller. In the prior art, it has usually been convenient to designthe mechanism so that the same setting of the individual adjustmentwhich produces a striking force of a certain magnitude for the lowercasecharacter will, when the type bar is shifted, produce a slightly greaterstriking force, on the average, for the uppercase character on the sametype bar. This provision is of benefit in most cases but is a serioushandicap in those instances where the upper-case character is smallerthan the lower-case character.

In the prior art, it has also been the practice to change the customaryarrangement of the keyboardiin order to reduce the number of suchinstances to a minimum, but the conditions still represent a substantiallimitation espe cially where freedom of choice in the keyboardarrangement is a significant consideration. In such instances, thepractice has been to set the individual adjustment at some compromiseposition with respect to the requirements of the two charactersinvolved, so that neither character has its optimum color density at thereference setting, one usually being too light and the other too dark,unless the relative importance of the two characters happens to be suchthat one or the other is exclusively favored.

This limitation can be overcome completely by, and it is a furtherobject of this invention to provide an improved structure for,incorporating additional provi sions to supply a separate andindependent set of individual and gradient control elements so that oneset of control elements is operative in the upper-case condition only,and the other set operative in the lower-case condition only. When thisis done, it then becomes practical to locate any character in anydesired position without sacrifice of quality.

It is a still further object of this invention to provide anirnprovedtype bar actuating mechanism having a convenient externally adjustableindividual control for regulating the striking force of the type bar inorder to vary the color density of the printed Work.

It is a still further object of this invention to provide an improvedarrangement of impression controls which are independently adjustable todetermine the striking force of each type bar and are movablesimultaneously to vary the striking force of all type bars as a group.

Still another object is to provide an improved mechanism which isadjustable to vary the striking force of each type bar in proportion tothe area of the character typed.

Another object is to provide an improved mechanism which is adjustableto subject a type bar to different controls when typing upper and lowercase characters.

It is a still further object of this invention to provide an improvedconstruction in which the control elements for effecting a uniform colordensity of type bar imprint, or for effecting any other desireddistribution of type bar striking forces, can be pre-assembled andpre-adjusted so as to reduce the cost of typewriter construction andadjustment. 7 p g It is yet another object of this invention to providean improved power driven typewriter with a substantially wider usablerange of uniform print density than has heretofore been available, andin which any character can be placed anywhere on the keyboard withoutsacrifice of quality. 7

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

Briefly, this invention relates to an improved type bar actuatingmechanism wherein the initial power impulse from a cam action isapproximately equal for all type bars, but wherein a motion multiplyingleverage shift takes place at a certain stage of the cam action tocontrol the resulting extent of power driven lift of the type bar andits complementary free flight distance, thereby to effect a controlledstriking force for each type bar, which striking force may be regulatedto be proportional to the size of the type character and the class ofwork to be done.

In the drawings:

Fig. 1 is a side elevational view of an individual type bar and themechanism utilized for its actuation.

Fig. 2 is a perspective view ofa cam support bar which is used toposition control cams-whichregulate the extent of power drive during aprint stroke.

Fig. 3 is a side elevation of a variety of control cams mounted on thecam support bar.

Referring to the drawing and more particularly to Fig. 1, a type bar 1having the conventional upper and lower case type faces 2' is shownmounted for rotation about a pivot wire 3 and for engagement with aplaten 4. The lower or lever arm 5 of the type bar 1 is connectedthrough a link 6 to an actuating mechanism 7 which, in turn, is drivenby a switch controlled continuously rotating power roll 3. A key bar orkey lever 9 is operable to place the mechanism 7 in driven relation withthe power roll 8 to effect a pull on link 6 and the subsequent rotationof the type bar 1 for a print stroke.

While the above and the following descriptions relate generally to onlyone type bar and its associated mechanism, it is to be understood thatthe same structure applies to all the type bars in a typewriter.

The actuating mechanism 7 comprises a cam lever or rockable member 10, atrip plate 11, a power cam or cam element 12, a control lever or portion13 and suitable inter-connecting structure.

Cam lever 10 is mounted for angular motion about a pivot 14. Ascam lever10 rotates clockwise, its outer arm 15, which is interconnected throughlink 6 to lever arm 5, exerts a pull on type bar 1 torotate itcounterclockwise about pivot wire 3 toward platen 4; A retarding spring16 maintains cam lever 10 normally in its rest position shown in Fig. l,and restores the cam lever 10 to its rest position after each type barprint stroke.

In order to effect the clockwise movement of cam lever 10 about itssupporting pivot 14, power cam 12, which has a serrated peripheral oractuating surface 17, is mounted on a stub shaft 18, supported bycontrol lever 13. An end of shaft 18 extends across an adjacent edge ofcam lever 10 to provide a bearing surface whereby, when power roll 8pushes on the serrated surface 17 of cam 12, shaft 18 simultaneouslypushes on cam lever 10 to rotate it clockwise about its pivot 14.

Control lever 13 is mounted for rotation in a plane parallel to camlever 10; Specifically, control lever 13 is rotatably mounted on aspindle or pivot 19 carried by cam lever 10. Then since shaft 18 iscarried by control lever 13, and since an end of shaft 18 initiallybears against an edge of cam lever 10, control lever 13 and cam lever10' initially tend to rotate as a unit about pivot wire 14.

Control lever 13 is provided with a finger 20 which is displaced fromspindle 19 at someconvenient distance. Finger 20 is positioned forengagement with the peripheral surface of a certain control stop or cam21 in such a manner that when finger 20 engages the surface of controlstop 21, further rotation of the control lever 13 about pivot 14 as aunit with cam lever 10 is blocked. This'engagement terminates the firststage of the driving cycle, during which the rise motion of power cam 12has been applied directly to earn lever 10 through shaft 18. Thereafter,if the rise of cam 12 continues to urge shaft 18 away from the powerroll, the point of engagement between finger 20 and stop 21 (hereinaftercalled check point A) becomes a new center of rotation for control lever13. As soon as control lever 13 begins to rotate about check point A, itexerts a torque on cam lever 10 through spindle 19, to rotate cam lever10 about its pivot wire 14. When thecenter of rotation of control lever13 shifts from pivot 14 to check point A, the surface of cam lever 10which had been in direct contact with shaft 18 becomes separatedtherefrom since cam lever 10 will move at a greater angular velocityafter check point A has been reached. The amount of increase in angularvelocity is a function of the inverse ratio of the radial distancebetween pivot 14 and spindle 19, to the radial distance between pivot 14and shaft 18. In terms of its ultimate geometrical effect one unit ofrise of power cam 12 has about twice as much effect on the type bar riseduring the second driving stage as-during the first stage. The manner inwhich the relationship between the two driving stages is varied tocontrol the striking force of the type bar will be describedsubsequently, v

Conditioning of actuating mechanism! Key lever 9 is mounted for pivotalmovement about an arbor or fulcrum wire 22 in response to a pressureapplied to a key button 23. The outer end of key bar 9 is supported in aguide comb 24 which is provided with individual springs 25 for restoringkey bar 9 to its rest position (Fig. 1) after it has been depressed fora type bar print stroke.

Key bar 9 has an abutment or lug 26 and a ledge 27 positioned forengagement with actuating mechanism 7. More specifically, trip latch 11which is mounted for pivotal movement about a stud 28, carried by camlever 10, is provided with an ear 29 which, in its rest position, isheld closely adjacent lug 26 by means of a restoring spring 30.Restoring spring 30 interconnects car 31 on cam lever 10 and car 31' ontrip plate 11.

Trip lever 11 is provided remotely from stud 28 with an actuatingsurface 32, against which the abutting surface 33 of cam 12 is normallyheld by a cam restoring spring 34, which interconnects cam 12 with anear 34' carried by cam lever 10.

With this structure, depression of key bar 9 permits lug 26 to act onshoulder 29 to pivot trip plate 11 about stud 28 whereupon actuatingsurface 32 pushes on abutting surface 33 of cam 12 to rotate the latterclockwise about its supporting shaft 18 until the serrated surface 17comes into engagement with continuously rotating power roll 8.

The structure of actuating mechanism 7 is such that after a completeprint stroke, which has heretofore been alluded to, spring 34 will havebrought cam 12 back into its rest position (Fig. 1). The abuttingsurface 33 will then be in engagement with actuating surface 32 of thetrip latch, but if key lever 9 is still depressed, then ear 29 will notreturn to its original position under lug 26. Instead, ear 29 will stopagainst ledge 27, whereupon pivot 28 moves forward in slot 35 extendingspring 30 in the process. In this condition, lug 26 cannot act on ear 29to rotate trip latch 11, consequently a second print stroke of thatparticular type bar cannot take place so long as the key bar is helddepressed. Upon release of the key bar 9, however, the restoring spring30 pulls trip latch 11 upwardly to the left until it is again positionedfor contact with lug 26, whereupon subsequent depression of the key bar9 will condition actuating mechanism 7 for another type bar printstroke.

Impression control Referring again to actuating mechanism 7, it has beenpointed out that it not only rotates type bar 1 for a print stroke, butalso, in combination with stop 21, controls the striking force withwhich type bar 1 contacts the platen.

In all cases, the type bar is driven positively up to some desiredpoint, through the operation of the mechanism which has been described,after which cam surface 17 is separated from power roll 8 so that thetype bar rise cycle is completed by means of the momentum which has beenimparted to the moving parts, especially the head of the type bar.

The operation of the impression control mechanism can best beappreciated by considering in some detail the three basic stages of typebar rise which are involved: (1) direct cam drive, (2) indirect camdrive, (3) free flight. Of these, the first two accelerate the type barto a height and velocity which are determined by the geometry anddynamic characteristics of the system; the third stage serves to fill inthe remaining distance, during which the type bar velocity is reduced bythe operation of retarding spring 16 and frictional forces. The totalexcursion of the type bar is the same in all cases, and consequently,the extent and duration of the third stage is, therefore, the complementof the first two stages.

In the mechanism here described, the final striking force of the typebar is determined by the duration of the first stage of the action whichin turn controls the subsequent stages. During the first stage, aspreviously described, cam lever 10 and control lever 13 rotate as a unitabout pivot 14 until finger 20 contacts stop 21 at check point A. As aresult of this motion, type bar 1 is lifted by an amount which isdirectly proportional to the initial clearance between finger 20 andstop 21.

It also has been shown that during the second stage of operation, anyfurther rise of cam surface 17 produces an amplified motion of cam lever10, so that an additional rise of the type bar then takes place, whichis substantially greater for each remaining unit of rise of power camsurface 17.

It, therefore, follows that if the total rise of cam surface 17 isutilized, such rise through suitable mechanism hereinafter described maybe divided in any desired proportion between the first stage ofoperation and the second stage, and that the point of division is afunction of the initial clearance between finger 20 and stop 21. Thisrelationship will be clearer if two extreme cases are consideredinvolving very large and very small clearances, as follows:

If this clearance (finger 20 to stop 21) is sufiicient to absorb theentire rise of cam surface 17, then the entire power-driven rise of thetype bar is provided by the first-- stage condition, and none by thesecond stage. In this case, the type bar may be power driven to aminimum point as indicated schematically in Fig. 1 by the lower caseletter a.

If, on the other hand, the initial clearance is reduced to zero, thefirst-stage condition is also reduced to zero, and the entire rise ofthe type bar is then produced by the amplified leverage of the secondstage of operation. Consequently, the type bar rises much farther underpower, toward the point indicated by the letter d.

By suitable choice of initial clearance, the division point between thefirst and second stages can be set wherever desired, so that the typebar can be driven to any desired intermediate level, such as thoseindicated in Fig. 1 by 5b,, c,

In any case, the time duration for the rise of cam surface 17 issubstantially the same, because .the same cam surface or cycle isemployed and the power roll surface speed is constant. However, itshould be noted that the operation as described above takes into accountonly the geometry of the mechanical elements. Under actual operatingconditions the masses and spring characteristics of the parts, inconjunction with the particular rotational speed of power roll 8,significantly influence the response of the mechanism, but do not changethe basic pattern, in which the type bar tends to follow the cam action,as described, until the power driven portion of the cycle is complete.At this point, the driving force of the cam drops off, but theacceleration which has already been given to the type bar continues tocarry it onward toward the platen. As the type bar goes into the thirdstage of its flight, cam 12 is lifted clear of the power roll and issnapped back into its rest position by spring 34. Also, for conveniencein description, it has been assumed that the full rise of the power camsurface 17 is employed dur'mg the first and second stages of operation.In practice this not always the case, since the actual point ofdisconnection is determined by a complex combination of dynamic factorswhich may sometimes result in the cam being lifted off the power rollbefore its maximum lift has been delivered.

As a result of the sequence of events indicated above, the type bar israised through stages 1 and 2 by means of the power derived from therise of cam surface 17. At the close of stage 2, the type bar hasachieved a certain height and velocity. From then on, it can onlydecelerate. The deceleration stage also supplements the controlmechanisms of the first two stages in determining the final strikingforce of the type bar, because a type bar which is operating with a highpower cut-off point will have a short deceleration distance and a-veryheavy striking force, whereas the same type bar when operating with alow power cut-off point will have a long deceleration' distance whichwill tend tofurther reduce the final striking; force.

Individual control From the foregoing; it is evident that the finalstriking force of the type bar is basically determined; by the initialclearance existing between finger 2t) and stop 21, and that the strikingforce increases as the clearance decreases'and vice versa. It is,therefore, possible to pro duce any desired striking force for each typebar within the design limtis of the machineif' suitable means ofestablishing and varying the clearance are provided for each type bar. v

The final object is then twofold: (l) to compensate for those conditionswhich may tend to limit the range or degrade the quality of impressionin work being done, (2) to permit the operator to select an impressionlevel suited to the character of the work being done. These objects canbe achieved by suitable design of the, adjustable cam stops 21 and therotatable bar 36 on which they are mounted.

With a control cam 21 having a slope of constantly increasing radiussuch as that shown in Fig. 1, it follows that since the height to whicha type bar is driven under power is inversely proportional to the atrest clearance between finger 20 and the surface of control cam 21, thestriking force for any type bar is controlled byvarying the point ofcontrol cant 21 which engages finger 20.

In order to provide for the ready adjustment of earns 21, each cam isformed of a resilient material and in an arc of slightly greater than180. The cam is provided with a number of radially inwardly extendingfingers 21a which support the cam surface and which frictionally gripand hold the stop to the control bar. Control bar 36, in turn, has aplurality of transverse peripheral grooves 37 (see Fig. 2) which arearranged to position a control cam in alignment with each of the fingers20 respectively. With this structure of the cam 21 and grooves 37, thecam can be rotated so that any point on its periphery, for example,points a through d (Fig. 1) can be aligned for contact with the finger20. One of the fingers 21a of control cam 21 has a serrated surface ordetent 21 which hooks into one of a plurality of longitudinal grooves36' in bar 36.

With the construction of the parts described, it can be seen that theforce with which a type head hits the platen is selectively variable foreach key. That is, with reference to Fig. 1, it is possible to cut offthe power stroke of the print character at a point a, for example, bysetting control cam 21 so that point a engages finger 20.

.Likewise,-it is possible to cut otf the power stroke of' the printcharacter In at the point at by setting control cam 21 so that point dengages finger 29. It follows that this improved type bar controlpermits the regnilation of the striking force for each type bar, andconsequently, the level of color density or shade of each type charactercan be individually controlled by placing detent 21 in any one of thelongitudinal grooves 36.

Group control While the above described individual control constructionprovides for selective control of uniform color density for each typedcharacter under one set of conditions, it has been pointed out that thetypist may wish to raise or lower the striking force of all the typecharacters as a group so that a greater force will be available forprinting a plurality of carbon copies than that which she would use toprint a single carbon copy or for preparing a plate or stencil which mayrequire a very light impression. To efiect this group control, it issimply necessary to provide for the rotation of thecontrol cam supportshaft 36 so as to increase or decrease the distance between all; of the.fingers 20 and. allot the control cams 21, at one time.

One typical mechanism for effectinga 'groupco'ntrol is shown in Fig. 2-wherein a crank arm 55' is secured for Gradient control At this point,reference'is' made tothe fact that changes in imprint force should beproportional to the areaof the printed character. change in colordensity, there should be a greater change in the imprint force of alargeletter such as the m thanthe change required for a small charactersuch asthe It has been explained that through the use of the controlcams 21 the rate of change in type barlift and-imprint force iscontrolled by the slope of the cam surf-ace (i. e. thedistance'betweenfinger 20 and thesurface of cam 21 is thus controlled).It follows, therefore, that in orderfor the-imprint force change for alarge character to be greater than the force change for a smallcharacter, a cam of greater slope should be employed for the largecharacters than that used for the small character. In practice, it hasbeen found desirable to use three or four sets of cams, each having adifferent slope (see Fig. 3). In this manner, a control cam from one ofthe sets is chosen for each character soas toeffect a rate of change inimprint force substantially proportional to the area of the character tobe printed; This is called gradient-control, because its effects thegradient of the striking force. Gradient control insures that when thetypist selects the printing level she desires, regardless of whether itis light, medium 'or heavy, allof the type characters will print withsubstantially the same degree of color density, regardless of'theirsize.

Upper and lower case control It has been pointed out that one of theobjects of this invention is to provide a uniform density contnol notonly individually and collectively, but also for upper and lower casecharacters. It was mentioned, for example, that while many of the, uppercase characters are, larger than the lower case characters, so as tocall for a, certain greater impact force than that required for thelower case character, there is not. auniform ratio of character areabetween upper and lower case characters, and in some cases the ratio. isreversed. Consequently, any force multiplying factor that can beutilized to exert a, general increase in the. print force of the uppercase letters would be detrimental to uniform, shade or color densityparticularly with respect to the characters usually located in the uppercase positions on the type bars carrying the Arabic numerals.

It is apparent, therefore, that it is not sufficient to use only one setof control cams 21 to regulate individual control, group control a dgradient control. In this improved arrangement, the structure is such asto provide a uniform pressure of imprint for both upper and lower casecharacters irrespective of the relative sizes between the upper andlower case positioned characters. This uniform pressure is brought aboutby providing a second control cam 3'8'('Fig. 2) constructed similarly tocontrol earns 21 for each of the actuating mechanisms 7'. Specifically,for each actuating mechanism 7, a second control cam 38 is positionedimmediately adjacent the control cam 21 to permit the finger 20 normallyto engage control. cam 21, but atthe time of basket shift-.-that is forupper case printing-the control camshaft 36' is shifted axially Forexample, to produce an equal-- so as to present the second cam 38 inposition for engagement .with the finger of the actuating mechanism 7.

'Fig. 2 shows a preferred method of producing the axial shift in controlshaft 20. Specifically, the control shaft 36 is axially movable by anaxial pressure produced at its opposite ends. For example, one end 40has an extension 41 for engagement with a bushing 42 which extends fromthe side wall of the typewriter. The opposite end 43 includes a notchedcollar 44 which engages a shaft 45. Shaft 36 is biased by a spring 46,which tends to urge extension 41 into the bushing 42. The constructionof the notched collar 44 of the control cam shaft and its mounting shaft45, is such as to permit rotation of the control cam shaft 36 about itsaxis while maintaining the bias in spring 46.

In order to control the axial position of shaft 36 and hence, which ofthe control cams is positioned for engagement with fingers '20, abellcrank 48 is mounted on a spindle 49 (fixed to the side wall of thetypewriter), for rotation in response to axial displacement of aconnecting rod 50 which interconnects an arm 51 of the bellcrank 48 withthe typewriter basket (not shown). The oppositearm or engaging arm 52 ofthe bellcrank 48 is provided with a shoulder 53 which is positioned incontact with a ledge 54 on control cam shaft 38. With this structure,when the shift key of the typewriter is depressed to lower the basket ina manner well-known in the art, shaft 50 is moved axially downward torotate bellcrank 48 counterclockwise whereupon the shoulder 53 pushes onledge 54 of control shaft 36 and moves it in opposition to the bias ofspring 46, whereby the upper case control cam 38 is positioned forengagement with the finger 20 of control lever 13.

An incidental benefit derived from the construction of the shaft 36 andits mounting lies in the fact that all the control cams 21 and 38 can bepre-assembled on the shaft before installation in the typewriter. Thatis, once a setting for each control cam in a typewriter has beendetermined, the same setting can be used for any other similar machinein an assembly line. Accordingly, a subassembly may be used to reducematerially the cost of installation which now exists in conventionalmachines (in existing machines, the type bar drive control had to be setfor each type bar after a machine had been assembled).

In summary, to overcome the objections of the past type bar actuatingmechanisms, this improved structure has been provided in which theeffective power cam rise is nearly the same regardless of the colordensity or shade of imprint which is to be produced. The initialresponse of the system is the same for all conditions, but after anoptionally variable amount of motion at a basic rate, a leverageshifting factor is introduced which multiplies the amount of type barmotion produced by whatever amount of cam rise still remains. A simple,.but comprehensive combination of adjustments, has been provided whichpermits complete control of the color densities of all characters on thekeyboard at all levels of impression.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intention,therefore, to be limited only as indicated by the scope of the followingclaims.

What is claimed is:

l. A power mechanism for typewriters and similar office machinescomprising power driving means, a type bar, a rockable member mounted todrive said type bar to a printing position, a power unit for operatingsaid rockable member, said power unit having an element ro- 10 tatablyengageable with said power driving means for driving engagement with thelatter, means for imparting an initial rotational movement to saidelement to engage it with said power driving means, a pair of adjustablecontrol means positioned for selective engagement with'said power unitto vary respectively the degree of power driven operation of saidrockable member, and means for selectively engaging said control meanswith said power unit.

2. In a power mechanism for typewriters and similar oflice machinescomprising, in combination, power driving means, a type bar having apair of type faces thereon, a shift device for selecting the type faceon said type bar to be printed, and a rockable member mounted to drivesaid type bar to a printing position, a power unit for operating saidrockable member, said power unit including an element rotatablyengageable with said power driving means for driving engagement with thelatter, means for imparting an initial rotational movement to saidelement to engage it with said power driving means, and a pair ofadjustable control means positioned for selective engagement with saidpower unit in response to the operation of said shift device to varyrespectively the degree of power driven operation of said rockablemember.

3. In a power mechanism for typewriters and similar office machinescomprising in combination, power driving means, a type bar having a pairof type faces thereon, a shift device for selecting the type face onsaid type bar to be printed, and a rockable member mounted to drive saidtype bar to a printing position, a power unit for operating saidrockable member, said power unit including an element rotatablyengageable with said power driving means for driving engagement with thelatter, means for imparting an initial rotational movement to saidelement to engage it with said power driving means, means to restoresaid element after disengagement from said power driving means, and apair of adjustable control means positioned for selective engagementwith said power unit in response to the operation of said shift deviceto limit respectively the degree of power driven operation ofsaidrockable member.

4. A power mechanism for typewriters and similar ofiice machines'comprisnig power driving means, a type bar, a rockable member mountedto drive said type bar to a printing position, a power unit foroperating said rockable member having an element rotatably engageablewith said power driving means for driving engagement with the latter,means for imparting an initial rotational movement to said element toengage it with said power driving means, means to restore said elementafter disengagement from said power driving means, and control meanspositioned for engagement with said power unit to vary the degree ofpower driven rotation of said rockable member, said control meanscomprising a control bar having an axis parallel to that of said powerdriving means and an adjustable control cam positioned on said controlbar to partially encircle the same and to have one peripheral point at atime positioned for engagement with said power unit.

5. A power mechanism for typewriters and similar office machinescomprising power driving means, a type bar, a rockable member mounted todrive said type bar to a printing position, a power unit for operatingsaid rockable member, said power unit having an element rotatablyengageable with said power driving means for driving engagernent withthe latter, means for imparting an initial rotational movement to saidelement to engage it with said power driving means, means to restoresaid element after disengagement from said power driving means, andcontrol means positioned for engagement with said power unit to vary thedegree of power driven operation of said rockable member, said controlmeans comprising a control bar having an axis parallel to that of saidpower driving means, an adjustable control cam positioned onv saidcontrol bar to partially encircle the same and to have one peripheralpoint at a time positioned for engagement with said power unit, andmeans for rotating said control be printed, and a rockable membermounted to drive saidtype bar to a printing position, a. power unit foroperating said rockable member having an element rotatably engageablewith said power roller for driving engagement with the latter, means toimpart an initial rotational movement to said elements to engage it withsaid power roller, and control means positioned for engagement-with saidpower unit to vary the degree of power driven operation of said rockablemember, said control means comprising a control bar having an axisparallel to that of said power roller, a pair of adjustable control camsjuxtapositioned on said control bar for selective engagement withsaidpower unit, and means interconnecting said control bar and saidshift device to axially displace said control bar in response to the,operation of said shift device to select which of said control cams isengageable with said power unit.

7. In a power mechanism for typewriters and similar office machinescomprising, in combination, power driving means, a type bar having apair of type faces thereon, a shift device for selecting the type face:on said'type bar to be printed, and a rockable member mounted to drivesaid type bar to a printing position, a power unit for operating saidrockable member, said power unit having an element rotatably engageablewith said power driving means for driving engagement with the latter,means for imparting an initial rotational movement tosaid element toengage it with said power driving means, means to restore said elementafter disengagement from said power driving means, and control meanspositioned for engagement with said power unit to vary the degree ofpower. driven operation of said rockable member, said control meanscomprising a control bar having an axis parallel to that of said powerdriving means, a pair of adjustable control cams juxtapositioned on saidcontrol bar for se lective engagement with said power unit, meansinterconnecting said control bar and said shift device to axiallydisplace said control bar in response to the operation: of said shiftdevice to select which of said cams is engageable. with said power unit,and means to rotate said control bar to vary the section of said controlcams positioned for contact with saidpower unit.

8. In a power mechanism for typewriters and similar ofiice machinescomprising, in combination, power driving means, a type bar having apair of type faces thereon, a shift device for selecting the type faceon said type bar to be printed, and a rockable member mounted to drivesaid type bar to a printing position, a power unit for operating :saidrockable member, said power unit having an element rotatably engageablewith, said power driving means for driving engagement with the latter,means to impart an initial rotational movement to said element to engageit with said power 'driving means, and control means positioned forengagement with said power unitto vary the degree of power drivenoperation. of said rockable member, said control means comprising. acontrol bar, a pair of stop means. positioned on said control bar forengagement one, at a time with said power unit, and meansinterconnecting said shift device and said controlbar to select which ofsaid stop means is engageable with said power unit.

9. In a power mechanism for typewriters and similar office machinescomp-rising power driving means, a type bar having a type face thereon,and a. rockable member mounted; to drive said type bar to a printingposition, a power unit for operating; said rockable member comprisingan, element rotatably engageable withsaid power driving means fordriving engagement with the latter,

12 means. to, impart an initial rotational movement to said element toengage it with said power driving means, and control means positionedfor engagement with said power unit to-vary the degree, ofi powerdriven, operation of said rockabilemember, said'control meanscomprisinga control bar having an axis parallel to that. of said powerdriving means, and an adjustable control ca m positioned on said controlbar to have one point at a time positioned for enrgagement with saidpower unit, said control cam having a slope rate commensurate with thearea of said type face relative to the average area of all the typefaces of said typewriter.

10. A power mechanism for typewriters and similar ofiicemachinescomprisingpower driving means, a type bar, a rockable membermounted to drive. said type bar to a printing position, and a power unitfor operating said rockabie member comprising a control portion pivotedon said rockable member, .a cam element pivoted onsaidv control portionand rotatable through a cycle for driving pivot being in direct drivingrelation with said rockable member to drive it at one rate until thepivotal movement of said control portion has been blocked, and controlmeans engaged by said controlportion duringrthe. course of the rotationof said cam element by the power driving means to block the pivotalmovement of said control portion thereby to vary the extent of directdrive between. said cam element pivot and said rockable member.

11. In a power mechanism for typewriters and similar office machinescomprising, in combination, power driving means, a type bar having apair of type faces thereon, a shift device forselecting the type face onsaid type to be printed, and a rockable member mounted to drive saidtype bar to a printing position, a power unit for operating saidrockable member comprising a control portion pivoted on said rockablemember, a cam element pivoted on said control portion and rotatable fordriving relation with said powerdriving means, and control means engagedby said control portion during the course of rotation of said element bythe power driving means for .varying the degree of power drivenoperation of said rockable member,.said control means comprising acontrol bar, a pair of stop meanspositioned on said control bar forengagement one at a time with said control portion, and meansinterconnecting-said shift device and said control bar to selectrwhich'of said stop means is engageable with said control portion.

12. In a power mechanism for typewriters and similar ofiice machinescomprising power driving means, a type bar having a pair of type facesthereon, a. shift devicev for selecting the. type face on said; type barto be printed, and a rockable member mounted to drive said type bar to aprinting position, a power unitfor operating said rockable membercomprising. a control portion pivoted on said rockable member, a cam.element pivoted. onsaid control portion and rotatable for drivingrelation with said power driving means,.said' cam element pivot being indirect driving relation with said rockable. member to drive it. atv onerate until the. pivotal movement of said control portion has beenblocked, and control means engaged by said control portion during thecourse of the rotation of said element by. the power driving means'toblock the pivotal movement of said control portionthereby to vary theextent of direct drive betweensaid cam element pivot and said rockablemember, said: control means comprising a control bar, a pair of'stopmeans positioned on said control bar for engagement one at a time withsaidcontrol portion, and means interconnecting said shift deviceand saidcontrol bar to select which of said stop means, respectively, isengageable with saidcon-- trol portion.

13. A power mechanism for typewriters and similar ofiice machinescomprising a power roller, a typebar, a rockable member mounted to drivesaid type; bar to: a. printing-position, a power unit for operatingzsaidrockable: member comprising. a, control. portion pivoted: on the.

13 latter, a cam element eccentrically pivoted on said control portionand rotatable through a cycle for driving relation withsaid powerroller, means to initially rotate said element until its smallest radiusis gripped by said power roller, said cam element pivot being in directdriving relation with saidrockable member to drive it at one rate untilthe pivotal movement of said control portion has been blocked, and beingin indirect driving relation with said rockable member to drive it at agreater rate after the pivotal movement of said control portion has beenblocked, and control means positioned for engagement by said controlportion to block the pivotal movement of said control portion therebyduring the course of the rotation of said element by the power rolllerto vary the extent of direct drive between said cam element pivot andsaid rockable member.

14. A power mechanism for typewriters and similar oflice machinescomprising a power roller, a type bar, a rockable member mounted todrive said type bar to a printing position, and a power unit foroperating said rockable member comprising a control portion pivoted onsaid rockable member, a cam element eccentrically pivoted on saidcontrol portion and rotatable for driving relation with said powerroller, said cam element pivot being in direct driving relation withsaid rockable member to drive it at one rate until the pivotal movementof said control portion has been blocked, and being in indirect drivingrelation with said rockable member to drive it at a higher rate afterthe pivotal movement of said control portion has been blocked, andcontrol means positioned for engagement by said control portion duringthe course of the rotation of said element by the power roller to blockthe pivotal movement of said control portion thereby to vary the extentof direct drive between said cam element pivot and said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, and an adjustable control cam positioned onsaid control bar to have one section at a time engageable with saidcontrol portion.

15. In a power mechanism for typewriters and similar ofiice machinescomprising a power roller, a type bar having a pair of type facesthereon, a shift device for selecting the type face on said type bar tobe printed, and a rockable member mounted to drive said type bar to aprinting position, a power unit for operating said rockable membercomprising a control portion pivoted on said rockable member, a camelement pivoted on said control portion and rotatable through a cyclefor driving relation with said power roller, said cam element pivotbeing in direct driving relation with said rockable member to drive itat one rate until the pivotal movement of said control portion has beenblocked, and control means engaged by said control portion during thecourse of the rotation of said element by the power roller to block thepivotal movement of said control portion thereby to vary the extent ofdirect drive between said cam element pivot and said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, a pair of adjustable control camsjuxtaposition-ed on said control bar for selective engagement with saidcontrol portion, and means interconnecting said control bar and saidshift device to axially displace said control bar in response to theoperation of said shift devicce to select which of said cams isengageable with said control portion.

16. A power mechanism for typewriters and similar ofiice machinescomprising a power roller, a type bar having a pair of type facesthereon, a shift device operable to select the type face on said typebar to be printed, a rockable member mounted to drive said type bar to aprinting position, a power unit for operating said rockable membercomprising a control portion pivoted on said rockable member, a camelement eccentrically pivoted on said control portion and rotatablethrough a cycle for driving relation with said power roller, means toinitially rotate said element until its smallest radius is gripped bysaid power roller, said cam element pivot being in direct drivingrelation with said rockable member to drive it at one rate until thepivotal movement of said control portion has been blocked, and being inindirect driving relation with said rock-able member to drive it at ahigher ratefafter the pivotal movement of said control portion has beenblocked, and; control means engaged by said control portion during thecourse of the rotation of said cam element by the power roller to blockthe pivotal movement of said control portion thereby to vary the extentof direct drive between said cam element pivot and said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, a pair of adjustable control camsjuxtapositioned on said control bar for selective engagement with saidcontrol portion, means interconnecting said control bar and said shiftdevice to axially displace said control bar in response to the positionof said shift device to select which of said cams is engageable withsaid control portion, and means to rotate said control bar to vary thesection of said earn positioned for contact with said control portion,each of said control cams having a slope rate comensurate with the areaof its associated type face on said type bar, relative to the averagearea of all of the type faces of said typewriter.

17. A power mechanism for typewriters and similar oflice machinescomprising a power roller, a type bar, a rockable member mounted todrive said type bar to a printing position, a power unit for operatingsaid rockable member comprising a control portion pivoted on saidrockable member, a cam element pivoted on said control portion androtatable for driving engagement with said power roller thereby .toeffect a rotation of said control portion and the rotation of saidrockable member, and control means engaged by said control portionduring the course of rotation of said element by the power roller forvarying the degree of power driven operation [of said rockable member.

18. A power mechanism for typewriters and similar ofiice machinescomprising a power roller, a type bar, a rockable member mounted todrive said type bar to a printing position, and a power unit foroperating said rockable member comprising a control portion pivoted onsaid rockable member, a cam element pivoted on said control portion androtatable for driving engagement with said power roller thereby toeffect a rotation of said control portion and the rotation of saidrockable member, and control means engaged by said control portionduring the course of rotation of said element by the power roller forvarying the degree of power driven operation of said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, and an adjustable control cam positioned onsaid control bar to partially encircle the same and to have oneperipheral portion at a time engageable with said control portion.

19. A power mechanism for typewriters and similar ofiice machinescomprising a power roller, a type bar, a rockable member mounted todrive said type bar to a printing position, and a power unit foroperating said rockable member comprising a control portion pivoted onsaid rockable member, a cam element pivoted on said control portion androtatable for driving engagement with said power roller thereby toeffect a rotation of said control portion and the rotation of saidrockable member, and control means engaged by said control portionduring the course of rotation of said element by the power roller forvarying the degree of power driven operation of said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, an adjustable control cam positioned on saidcontrol bar to partially encircle the same and to have one section at atime engageable with said control portion and means to a rockable membermounted to drive said type bar to a printing position, a power unit foroperating said rockable member comprising a control portion pivoted onsaid rockable member, a cam element pivoted on said control portion androtatable for driving engagement with said power roller thereby toeffect a rotation of said control portion and the. rotation of saidrockable member, and control means engaged by said control portionduring the course of rotation of said element by the power roller forvarying the degree of power driven rotation of said rockable member,said control means comprising a control bar having an axis parallel tothat of said power roller, a pair of adjustable control camsjuxtapositioned on said control bar for selective engagement with saidcontrol portion in response to the operation of said shift device, eachof said control. cams having a slope rate commensurate with the arealofits associated type face on said type bar relative m the average areaof: allthe type faces of said. machine.

- 21.. In a power mechanism for. typewriters and similar oflice.machines, a type element having a pair of type facesthereommeans-drivingsaid type element to print position, shifting means for determiningwhich of said type faces is to be printed, and a'pair of control stopsengageable with said type elementdriving means in response to the opera--tion of said shifting means to control the imprint force of said typefaces respectively.

References Citedin the tile of this patent UNITED STATES PATENTS SchulzeFeb; 16, 1926

